The present invention relates generally to electronic display indicators, and more particularly, to an electronic liquid crystal display indicator having an enlarged display screen viewing area.
One example of such displays are electronic flight indicators which are required on most aircraft, to inform the pilot and, if applicable the copilot of the aircraft, of various information to assist in flying the aircraft. Military aircraft, commercial aircraft and even personally owned airplanes include electronic flight indicators in the instrument panels of the aircraft. Two common electronic flight indicators are: a horizontal situation indicator ("HSI"); and, an attitude direction indicator ("ADI"). For many years HSI and ADI consisted of electro-mechanical devices which used several internal gears powered by an electric motor(s) to drive the displays seen on the screen. These devices have been known to be prone to failure after just a few hundred hours of operation. A need exists for a more reliable design for electronic flight indicators.
Most military and commercial aircraft of today have a standard aircraft instrument panel dimension for each flight instrument. This is sometimes referred to as an ARINC cutout. In other words, the ARINC cutout for an ADI or HSI has already been predetermined by industry standards. Thus the dimensions of an ADI or HSI cannot exceed preexisting space limitations on the aircraft instrument panel. Prior to the present invention it was thought that the display screen of an HSI or ADI was fixed in size at approximately 3.4 inches.times.2.8 inches, since this has been substantially the maximum area for the screen display to occupy in the standard ARINC cutout for ADI and HSI. Due to the importance of making an ADI or HSI easily visible to a pilot or copilot it is advantageous to increase the size of the screen display. Prior to the present invention this was thought to be unachievable due to the space limitations established by the standard ARINC cutout dimensions on an aircraft instrument panel. In one preferred embodiment of the present invention a 60 percent increase in the screen display viewing area of an ADI or HSI is achieved, while maintaining the same body or chassis dimension of known ADI or HSI to reside within a standard ARINC cutout. The increased viewing area can also enable other flight indicators to be displayed on an HSI or ADI display glass.
The ADI and HSI of the present invention incorporate liquid crystal display (LCD) technology, known to those of ordinary skill in the art, to produce the visible display on an ADI or HSI. This particular technology, which may be an active matrix liquid crystal display (AMLCD) consists of a series of rows and columns of red, green, and blue dot transistors sandwiched between two glass panels. A liquid crystal fluid is activated by a voltage which changes the plane of polarization causing the dot transistors to emit light in the colors of red, green or blue or a mixture thereof. There can be several hundred columns of dots going across the display as well as hundreds of vertical rows of dots which can result in over one hundred thousand individual transistor switch dot triplets of red, green and blue. The liquid crystal display is driven by electronics contained within the body or chassis of the ADI or HSI assemblies.
The present invention provides a new and enlarged viewing display on an electronic flight indicator to be installed in a standard ARINC cutout on an aircraft instrument panel. The electronic flight indicator includes a body or chassis portion, a front mounting flange, and a bezel assembly on the face of the flight indicator. The present invention places the display screen into the front mounting flange and the bezel which reside just outside (the cockpit side) of the standard ARINC cutout on the instrument panel. By moving the display screen to the front flange an increased viewing area can be obtained.
The present inventor had to overcome certain obstacles to obtain a working display in the front flange of the flight indicator assembly. First, to provide light to the entire viewing area on the screen it became necessary to move the backlight, which prior to the present invention existed in the body or chassis of the flight indicator, to a position immediately adjacent to the rear of the bezel and just behind the display screen. Second, a display interface was needed to make contact with the glass, now moved to the front mounting flange. The display interface enables the dot transistors to receive electronic signals from the interface electronics in the chassis which have processed signals from various aircraft sensors.
It is recognized that the present invention is useful in other display indicators besides those found in aircraft. Similar indicators may be found in submarines, tanks, ships, and other vehicles. The present invention will be better understood from the following description of the drawings and detailed description of the preferred embodiments.